The role of an extrahypothalamic thermoregulatory mechanism in the pontine tegmentum, which inhibits heat-gain responses, on thermoregulation during wakefulness and sleep will be examined. Thermoregulatory responses to different ambient temperatures will be studied in cats, before and after inactivating the inhibitory are in the ventromedial pontine tegmentum. The inactivation will be done permanently by placement of electrolytic or chemical lesions or transiently by microinjections of a local anesthetic. Cats will be chronically implanted to record EEG, EOG EMG, core and subcutaneous temperatures. For microinjection studies, cats will also be implanted with bilateral cannulae. The possible role of this pontine thermoregulatory area on the suppression of thermoregulation during paradoxical sleep will be examined in cats in which the usual atonia has been abolished by means of small, dorsolateral pontine leions, the rationale being that such cats should be capable of behavioral thermoregulatory responses. This preparation has previously proved useful in studying the role of atonia in state-related changes in shivering and piloerection. These studies would contribute to our understanding of the brainstem control of thermoregulatory responses not only in physiological conditions, but also in a variety of pathological conditions, such as pathological alterations in body temperature which occur following brain damage or hemorrhage around the brainstem.